1. Field of the Invention
The invention relates to the dyeing of denim cotton yarns. Specifically, the invention relates to dye compositions for dyeing cotton yarns such as denim cotton warps, to a dyeing process of cotton yarns using the dye compositions, and to dyed articles colored with the dye compositions.
2. Description of the Prior Art
Denim is popular for its touch and stoutness of cotton as textures for clothing and is used widely as work clothes, women's slacks, children's garments, etc.
Jeans made of denim have been in expanded use as clothing called blue jeans. The reason why blue jeans are used so widely is that the textures colored with indigo dyes are preferred for their unique tone of color and for the variation of the tone with the passage of time, and that the development of clothing giving importance to the feeling which makes the use of the variation is made possible. However, recent diversification and individualization of fashion have increased the demand not only for blue jeans but also for what is called color jeans, such as, those of yellow, red and black. Consequently, there has been a desire to dye denim, which is the texture for jeans, with various color tones ranging from grey to black. In dyeing cotton warps to prepare color denim, which is demanded by the vogue of color jeans, sulfur dyes, vat dyes, reactive dyes and naphthol dyes are being used. However, color jeans dyed with these dyes are different in properties from indigo-dyed articles, and hence the value of their commercial products ranging from dyed textures to clothing are different from those of conventional blue jeans.
As described above, blue jeans are preferred as clothing for their specific tone of color and other properties and these characteristics are also desired for color jeans. Sulfur dyes, vat dyes, reactive dyes and naphthol dyes do not impart such characteristics to their dyed articles. For instance, when the above-described dyes are used, the dyeing behavior of these dyes are too different from that of indigo dyes to process yarns in a rope-dyeing plant for blue jeans which employs indigo that has conventionally been in wide use. Therefore, these dyes are hardly applicable in such dyeing operation.
Moreover, with these dyes, decoloring effects cannot be expected by bleaching them with chlorine. As a result, in bleaching black denim composed of cotton warps colored with a black dye formed by blending indigo and ordinary yellow and red threne dyes, the blue color alone is decolored leaving an orange color remaining, thus resulting in a significant impairment of its commercial value. In other words, with rope-dyed products using a mixture of an indigo dye with other dyes including sulfur dye vat dye, naphthol dye, reactive dye, etc., fading effects as observed with blue denim cannot be expected because these dyes, unlike indigo, exhibit very small decoloring effects when bleached with chlorine. Hence, their commercial values are extremely inferior.
As described above, dyes which exhibit a similar dyeing behavior and similar properties to indigo have not yet been disclosed. Consequently, neither a dyeing process of cotton yarns using a novel dye having such properties nor color jeans using denim cotton yarns colored with such a dye have been disclosed.